Planning Windows Phone 7 application

What are the steps for in planing and dev开发者_StackOverfloweloping a Windows Phone 7 application?

1. First design interface and write code
2. Expression blend and then VS 2010
3. First design layout in Photoshop then expression blend and then VS 2010
4. Write code first in VS 2010 (to achieve main goal) then design interface

What is the correct method?

1. I typically use a tool like Balsamiq to mock up my UI design
2. Once I am happy with the UI design, I design and code the entities to support my app
3. Once the entities are designed, I create ViewModel objects (I use MVVM).
4. With the ViewModel done, I create the UI for WP7.

Iterate through 1 to 4.

Once I am happy, I then use Blend to prettify the UI (add animations, states, etc).